Motorola's 68328, aka DragonBall, was designed in late 1990's for handheld computer such as the Palm. It is an highly integrated processor with a 68EC000 core. Among the peripheral is a LCD controller which was why I bought some in the first place 5+ years ago. To my dismay, I realized I've purchased the BGA version that's too difficult to prototype, but the price is right so I kept them for my 68K CPU collection.

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There is an interesting bootstrap feature on 68328 that supports serial communication with the processor and its peripherals without any external ROM/RAM. Only a dozen signals need to be connected to enable the bootstrap mode. Better yet, the software tool for interfacing in bootstrap mode is still available on the NXP website. So it is conceivable to hand wire a dozen wires to the tiny BGA and earn the bragging right of having power up the tiniest, minimalist 68K system, for what it's worth.

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This is the schematic for enabling the bootstrap mode. All is needed is hookup a 32.768Khz crystal , ground nEMUBKT while resetting and talk to the serial port, that's it. The initial baud rate is 9600, but bbug.exe changes it to 19200, it can even be configure to 115200. bbug.exe is a DOS program with a few basic commands, display memory, modify memory, load program, and go. This is a screen shot of 16 bytes memory in 0xFFFFFF00 being displayed.

Very nice!I'm surprised the crystal & capacitors network works so far away from the CPU. I think it has a zero-glue interface to DRAM. I'm particularly interested in how well it interface to LCD graphic display. I want to use it as my graphic engine.Is there a cheap source for 68EZ328? I saw 68VZ328 selling for $5 or less, but not 68EZ328.

Plasmo,I purchased MC68EZ328 with aliexpress. (https://www.aliexpress.com/)If you search, you will find several shops.I will use it when purchasing old parts.Although it may take time to arrive at the product, there is no problem as it is a hobby.

I connected the CPU board I made with 256 KB SRAM on the bread board and the operation was unstable.So I rebuilt the CPU board, wired the power supply and the crystal at the shortest distance, and attached a lot of capacitors.

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When connecting a new CPU board with 256 KB SRAM, the operation became stable.

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I will try to reassemble this circuit from the bread board to the universal board.Now I can run the 68k program.

Great! So now you can write a bootable monitor software, load and execute out of the RAM. Once that checked out, you can program a set of flash and boot up with it. Do you have plan to make pc board with your design?

I chose the memory check program as the first program to run on this system.The source code of the program was included in the ZIP file.We modified the source code slightly and created an S format file with the assembler of EASy68K.

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Since the memory implemented in the system uses two 256Kbits (32K × 8bits) SRAM chips, the memory space is 64Kbytes (0×0000 - 0×ffff).The program was placed at 0x2000, and it was confirmed that reading and writing to memory can be done normally until 0x4000-0xffff.

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I would like to create and run a simple monitor program in the same way. Next, I might implement FORTH.I finally want to run uClinux.Easy68k is a great tool. Thank you for exciting me.

I'm thinking of something small, about the size of a 600-mil 40-pin DIP that has the 68EZ328 BGA fitted under a 32-pin 600-mil 512KB RAM, 32KHz crystal, 3.3V regulator, and a serial port. Power comes from USB-to-serial adapter. Implemented on a 2-layer pc board that is very thin, 0.6mm, so I can solder the BGA over a hot plate (or skillet over fire). The pcb factory is shut down for Chinese New Year. It'll be 2 weeks before I can send the board out. Bill

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